The invention concerns a method and a device for crimping a stent onto a balloon of a balloon catheter, wherein the stent is arranged on the balloon in such a way that the outside surface of the balloon and the inside surface of the stent are in contact with each other in order to form a combination of balloon and stent, the combination being compressed to crimp the stent onto the balloon.
Methods and devices of this kind are known in the prior art. They serve to produce a combination comprising the balloon of a balloon catheter and a stent which is crimped on the balloon. That makes it possible to move the stent of reduced outside diameter at its desired position on the balloon by means of the catheter into the region of the stenosis to be dilated, and at the same time to hold the stent on the balloon in fixed relationship.
In the methods and devices known in the prior art, the stent, for crimping on the balloon, is compressed by radially inwardly acting forces until it is carried fixedly on the balloon, but can still be deployed by inflation of the balloon in order to be fitted into the internal vessel wall of a stenosis in order to support it. Such a method and a device are known, for example, from U.S. Pat. No. 5,836,952, to Davis (Nov. 18, 1998).
One disadvantage with the prior methods and devices is that the edges of the stents can stick out, or can be bent out, when the stent has to be passed in part through tight narrow vessel curvatures when the combination is inserted through the vessels of the body to the stenosis. When this occurs with regard to segmented stents, it is referred to as the xe2x80x9cfish scalingxe2x80x9d effect, and it results in damage to the internal walls of the corresponding vessels or in the stent coming into hooking engagement with the vessel wall and possibly being displaced on or being caused to slip off the catheter balloon, which can result in deposits or ruptures of the vessels.
Therefore an object of the present invention is to provide a combination of stent and balloon or a method and a device for crimping a stent on a balloon, which avoid the above-mentioned disadvantages and which securely bring the stent to its implantation location.
In accordance with the invention that object is attained by a method, a crimping device and a combinations as set forth in the accompanying claims.
The advantages of the present invention are in particular that the fish scaling effect can be avoided or reduced by the fact that the two axial ends of the stent are bent inwardly. As a result, in particular the edges of segments of the stent, which are arranged in succession in the axial direction of the stent, bear against the balloon, even in the procedure for inserting a catheter carrying the combination through narrow winding vessels. The risk of damage to the internal vessel wall is thus reduced, like also the thrust force required for inserting such a balloon catheter or such a combination. In addition, it is also advantageous that the invention provides that the adhesion between the stent and the balloon is increased so as to prevent the stent from inadvertently sliding off the balloon upon insertion of the combination into the vessel in the body.
Advantageous embodiments of the method and the device according to the invention use rollers or plates which are at an alternately increasing and decreasing spacing relative to each so that a combination of stent and balloon which is clamped and compressed between the rollers or plates is crimped to differing degrees along the longitudinal axis of the combination.
The invention can be carried into effect in a particularly advantageous manner by the rollers or plates being provided with a corrugated surface. If now a combination of stent and balloon is forced through between rollers of that kind, the stent is crimped onto the balloon more strongly by the crests of the corrugation than by the troughs of the corrugation. The same applies in regard to compression by means of two plates arranged in parallel relationship. In that case the mutually facing surfaces of the plates are also corrugated in a wave-like configuration in a regular sequence. For the purposes of crimping the stents the two plates are moved towards each other at the same time displaced uniformly relative to each, whereby the combination of stent and balloon is compressed and thus the stent is crimped onto the balloon.
As an alternative it is also possible to use special profiled rollers in 2-, 3- or multi-point rolling devices, straight as well as inclined, to produce the crimping effect. As a further alternative for the invention it is possible to use collet chuck devices with a specially shaped internal clamping liner or also dies which are shaped according to the desired crimping profile. Finally it is also possible to provide for irregular crimping in accordance with the invention with the stent being locally enclosed with aperture-like shutter members.
A further advantageous embodiment of the crimping device according to the invention is distinguished in that for the crimping operation the stent-catheter combination is positioned in an entry nip or pinch between a first roller and a second roller which is arranged in adjacent parallel relationship with the first roller, and there is compressed in the entry nip by means of a third roller arranged in substantially parallel relationship with the other two rollers, at least one of the roller being provided with a corrugated surface. For that purpose, the third roller is preferably driven in rotation about its longitudinal axis. In a preferred embodiment the first and second rollers are supported rigidly while the third roller is mounted pivotably about the first roller by means of a lever connecting the first and third rollers so that in that way the stent-catheter combination positioned in the entry nip between the first and second rollers is compressed and thus crimped in the entry nip by pivotal movement of the lever and the third roller.
Further advantageous embodiments of the invention are set forth in the appendant claims.